[U-Boot] [RFC PATCH 1/5] spl: dfu: add dfu support in SPL

[B, Ravi]

Hi Lucasz

Thanks for active support.

>> >> > 
>> >> > - Would it be hard to add SPL-DFU support also to BeagleBone
>> >> >  Black(am335x) (BBB) board? I'm asking since BBB is far more 
>> >> > pervasive than dra7x (and I might be able to cover SPL-DFU easily 
>> >> > with our new ptest (DFU) test suite).
>> >> >   
>> >> 
>> >> It's possible to extend this for other platform, but SPL size would 
>> >> be 152k.
>> 
>> >That was my point to reduce the size as much as possible and only 
>> >provide minimal functionality to fit the bill.
>> 
>> Since DFU is tighly coupled to u-boot infrastructure , the size will 
>> increase due to multiple dependencies to compile u-boot DFU source in 
>> SPL. Let me re-think on possibility and come back.

>If you would need any assistance, please let me know (I don't have dra7x, but I do have Beagle Bone Black).

The current implementation of dfu (drivers/dfu/dfu.c) relies on environment modules (getenv,setenv), and hash algo methods.
The mandatory modules for DFU includes USB(dwc3/musb), gadget, drivers/dfu, hash, environ modules.
Added to this mmc/sf support, with filesystem fat/ext4 would definitely increase the size.

I have tried minimal subset adding DFU-SF serial flash support alone in SPL, this itself increases SPL size to 30K+ (SPL size approx. 107KB for dra7x). 

But beagle bone IRAM would be around 64KB right? Definetly this will not fit.

Can we enable this feature for platform with minimum SRAM size of 160KB.
So SPL-DFU cannot be supported for platform less than 160KB (like am335x).

Any suggestion ?

Regards
Ravi